Rhythm device



J. H. HEARNE Dec. 12, 1967 RHYTHM DEVICE 2 Sheets-Sheet l Wwf@ mi f ,f W2

RV. Mm www mm u mmm www mlwlm mw www @m mmm www N NNN J. H. HEARNE RHYTHM DEVICE Dec. l2, 1967 2 Sheets-Sheet 2 Original Filed March 16, 1961 INVENTOR. 1 QSQM/Mfm .www n United States Patent O 3,358,069 RHYTHM DEVICE Joseph H. Hearne, Corinth, Miss., assignor to The Wurlitzer Company, Chicago, Ill., a corporation of Ohio Continuation of application Ser. No. 96,135, Mar. 16,

1961. This application Sept. 19, 1966, Ser. No. 580,504

18 Claims. (Cl. Sti-1.03)

ABSTRACT F THE DISCLOSURE Electronic apparatus for producing percussive musical eifects, such as drums, wood blocks, cymbals, etc., by means of electronic (generators to accompany melody played on lknown musical instruments such as electronic organs, pianos, etc.

This invention is concerned with the art of electrical music generation, and more particularly with the production of sounds of a percussive nature.

This is a continuation of application Serial No. 96,135, filed March 1-6, 1961, now abandoned.

As is well known, small dance bands or combinations for producing or playing popular music commonly employ a certain number of instruments to produce the melody. In addition, there preferably is a rhythm accompaniment, produced by one or more musicians operating with various percussive sound generators, such as drums, tom-toms, temple and wood blocks, claves, maracas, brushes, and cymbals. Such rhythm accompaniment is of a repetitive nature, diiiering in accordance with the nature of the music, i.e., fox trot, samba, cha-cha, etc. However, for any lgiven step or type of music, the repetition is the same, and the tempo generally remains constant throughout any given number, or at least for a substantial portion thereof.

Often in a small club or place of entertainment, the iinancial expense of a small orchestra is prohibitive. Thus in order to make dancing possible, a single musician may be hired to play an electronic organ, or other melody instrument to permit dancing. Unfortunately, such a single musician is ordinarly incapable of simultaneously producing a rhythm accompaniment, and dancers must lget along without the rhythm accompaniment. This is undesirable, and yet financial considerations may often make it the only solution.

Accordingly, it is an object of this invention to provide apparatus for producing a rhythm accompaniment synthetically.

More particularly, it is an object of this invention to provide electronic generating means for the sounds of a rhythm accompaniment.

More particularly, it is an object of this invention to provide keyed, damped oscillators of somewhat different characteristics to produce many of the sounds of a rhythm or percussive accompaniment.

Yet another object of this invention is to produce various percussive or rhythm a-ccompaniment sounds by means of a random noise or hiss generator connected to a single tuned circuit by means of a plurality of different amplifier devices having different transient characteristics.

Yet another object of this invention is to provide a tone coloring means in an electronic music generator comprising a resonant or tuned filter or tank frequency modulated at a very low audio frequency, or perhaps just sub-audio, to introduce shimmer to the sound.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. l is a schematic wiring diagram of a synthetic rhythm generator constructed in accordance with the principles of the present invention;

FIG. la is a diagram indicating the wave shape of the bass drum, for example;

FIG. 1b is a schematic diagram of a mechanical switching arrangement;

FIG. 2 is a detail circuit diagram showing a modification of the formant filter and frequency modulation thereof by means of a voltage sensitive capacitor;

FIG. 3 is a view similar to FIG. 2 showing a modification utilizing a capacitive diode;

FIG. 4 is a modification similar to FIGS. 2 and 3 and utilizing a varistor;

FIG. 5 is a schematic wiring diagram showing a means for reiteration of the percussive voices; and

FIG. 6 is a detail schematic view showing a simplified arrangement of the tuned or formant filter in the circuit.

Referring first to FIG. 1, and specifically to the upper left corner thereof, there will be seen a bass drum generator identified generally by the numeral 10. The bass drum generator comprises a phase lead oscillator includinlg a triode tube 12, conveniently forming one-half of a dual triode, as illustrated. The triode comprises a plate 14, a grid 16, and a cathode 18. The plate is connected through a plate load resistor 20 to a B+ supply line 22. The plate is also connected through a resistor 24 in series with a capacitor 26 to ground.

The cathode 18 is connected to a resistor 28, and thence to ground. A sliding tap 30 on the resistor is grounded.

The grid 16 is connected to a shunting grid resistor 32, and also to a capacitor 34. The capacitor 34 is further connected to a capacitor and to a resistor 38, the other end of which is grounded. The opposite side of the capacitor 36 is connected through a feed-back capacitor 38 to the plate 14, and is also connected to a resistor 40. The resistor 40 is connected through a resistor 42 to ground, and also through a capacitor 44 to a junction point 46.

The junction point 46 is connected through a resistor 48 to a bias supply line 50, which, by way of example', is normally maintained at -22 volts. The junction 46 also is connected through a capacitor 52 to ground, and through a resistor 54 to a keying contact or switch 56. The ykeying contact or switch 56 is adapted to ground the resistor 54, as indicated by the dotted line 58, and has been shown in somewhat unconventional fashion, since i-t is not an ordinary switch, but is representative of either or both a manual switch or a mechanical repetitive switch.

The cathode of the phase lead oscillator is degenerated by the resistor 28 and sliding tap 30 so that the circuit normally -will not oscillate. The capacitor 44 charges through the resistor 48 from thel negative bias line 50. When the keying switch 56 is grounded, the resistor 54 being of very low value relative to the resistor 48, the bottom of the capacitor 44 is substantially connected to ground, and a positive pulse is applied to the grid. This biases the oscillator into oscillation, and the oscillation decays as the charge on the capacitor 44 leaks olf through the resistor 42. A small amount of grid current is drawn at iirst, and this detunes the oscillator high from its nominal frequency of about 65 c.p.s. This is most desirable, since normally a bass drum has a fast attack, or high frequency, followed by a low frequency tail as the diaphragm returns the heavy beater and then continues in decadent vibration. It will be recognized that the initial impact of the beater on the diaphragm or drum head stretches the head greater than during normal vibration. In addition, the center of the drum head is acoustically shorted out by the beater.

The fundamental frequency s determined by the phase shifting network and associated resistors and capacitors.

3 The attack is determined by the resistor S4, the capacitor 52, the resistor 42, and the capacitor 44. The attack is rounded off slightly by the capacitor 26.

Reference should be had to FIG. la for a schematic representation of a representative wave form as produced by the bass drum generator 10. The precise amplitudes are not intended to be limiting, but it will be observed that there is a steep wave front from A to B, after which a regular frequency is developed. Thus, the horizontal distance on the time axis from B to C is one-half the distance from C to E, which is equal E to F, etc. However, the distance from A to B is only about one-fifth that from C to E. The initial kick of the discharging capacitor to the oscillator is sufficient that the oscillator at first draws a certain amount of .grid current, thereby detuning the oscillator high, and producing the steep wave front from A to B, with the short time, which is equivalent to a higher frequency.

As has been noted, the basic frequency of the bass drum generator is about 65 c.p.s. Those skilled in the art would no doubt be able to reproduce the constants necessary forthis, but illustrative values are set forth hereinafter for guidance:

Resistor 270,000 ohms. Resistor 24 680,000 ohms. Resistor 32 680,000 ohms. Resistor 38 470,000 ohms. Resistor 40 470,000 ohms. Resistor 42 100,000 ohms. Resistor 48 680,000 ohms. Resistor 54 10,000 ohms. Capacitor 26 .01 microfarad. Capacitor 34 .0016 microfarad. Capacitor 36 .0016 microfarad. Capacitor 38 .0016 microfarad. Capacitor 44 .068 microfarad. Capacitor 52 .047 microfarad.

In addition, the junction between the resistor 24 and the capacitor 26 is connected by a .047 microfarad capacitor 60 in series with a 470,000 ohm resistor 62 to a collector line 64. As will be apparent, all of the values heretofore set forth are illustrative.

Adjustment of the sliding tap 30 on the resistor 28 adjusts the ring time of the circuit, whereby the bass drum can be varied in effect from a large field drum to a rather small drum.

. A rst tom-tom generator 66 is shown immediately to the right of the base drum generator 10 in FIG. l, and comprises a degenerated oscillator of substantially the same type as the base drum oscillator. rl`he first tom-tom generator includes a triode tube 68, conveniently the second half of the tube 12, and the configuration of the parts in the input side of the circuit is the same as in the bass drum, except for certain circuit values.

The basic frequency of the first tom-tom generator is about 120 c.p.s., and to achieve this frequency, some of the constants are different than in the bass drum. For example, the charging resistor 70 is 330,000 ohms. The resistor 72 is 470,000 ohms. The feed-back and phase shifting capacitors 74, 76 and 78 are each 750 micromicrofarads. The remaining resistors and capacitors on the left side of the generator circuit are of the same value as in the base drum generator.

, On the right side or output side of the circuit, a capacitor 80 is included in series with the resistor 82 connected to the oscillator plate. The capacitor conveniently is .0047 microfarad, and the resistor 1.5 megohms. The capacitor 80 is connected to ground through a .001 microfarad capacitor 84, and the junction of these two Icapacitors os connected by a 680,000 ohm output resistor 86 to the collector line 64.

The tom-tom oscillator is provided with ground-out keying at 88, in the same manner as the bass drum generator. There is a second tom-tom generator generally identified by the numeral 90, and identical with the first torntom generator, except for circuit value. The frequency of this generator is 180 c.p.s., and it is believed that anyone skilled in the art can readily ascertain the correct values, which hence, are not set forth herein. Again, the second tom-tom generator 90 is provided with ground-out keying at 92.

A first temple-block generator 94 is shown immediately to the right of the second tom-tom generator in FIG. 1. This generator is intended to simulate wood templeblocks struck together, and comprises a phase-shift oscillator differing slightly from the bass drum and tom-tom oscillators. In particular, it includes a triode tube 96 having a cathode grounded through a resistor 98 which has a grounded sliding tap 100 thereon. The plate is connected to the B+ supply line 22 through a load resistor 102, and is also connected to a feed-back capacitor 104. The

capacitor 104 is connected at a junction 106 to a capacitor' 108, which in turn is connected through a resistor to the collector line 64. The junction of the capacitor 103 and resistor 110 is also shunted to ground through a resistor 112.

The junction 106 is connected through a resistor 114 to a grounded capacitor 116. The junction between the resistor 114 and capacitor 116 is connected through series resistors 118 and 120 to the grid of the tube 96. The junction between the resistors 118 and 120 is shunted to ground through a capacitor 122. The junction between the resistors 114 and 118 is connected to a resistor 124 leading to a grounded resistor 126. The junction between the resistors 124 and 126 is connected through a capacitor 128 to a charging resistor 130 connected to the negative bias line 50, and also to a switch resistor 132. The resistor 132 is connected to a ground-out key switch 134, as previously discussed, and this switch and resistor are shunted to ground by a capacitor 136.

The frequency of the temple-block generator is about 600 cycles, and it is thought that one skilled in the art readily can supply the necessary values. However, by way of example, the following values are set forth:

Resistor 98 5,000 ohms. Resistor 102 100,000 ohms. Resistor 110 18,000 ohms. Resistor 112 4,700 ohms. Resistor 114 330,000 ohms. Resistor 118 680,000 ohms. Resistor 120 68,000 ohms. Resistor 124 1 megohm. Resistor 126 100,000 ohms. Resistor 130 1 megohm. Resistor 132 180,000 ohms. Capacitor 104 .047 microfarad. Capacitor 108 .0068 microfarad. Capacitor 116 .0027 microfarad. Capacitor 122 .0022 microfarad. Capacitor 128 .002 microfarad. Capacitor 136 .01 microfarad.

A second temple-block generator 138 is shown immediately to the right of the rst temple-block generator in FIG. 1. This generator is of the same nature as the first temple-block generator 94, except that the constants are selected to provide a frequency of 900 cycles, Again, groundout keying is provided at 140.

A wood-block generator 142 is shown immediately to the right of the second temple-'block generator, and is provided with ground out keying at 144. The wood-block generator is the same as the two temple block generators, but the constants are chosen to provide a frequency of 1200 c.p.s.

`Returning to the left side of FIG. 1, and immediately below the bass drum generator, there is shown a clave generator 146. This generator is lthe same as'the templeblock and wood-block generators, but with the constants chosen to provide a frequency of 2,000 c.p.s. A groundout key switch is provided at 148.

As noted heretofore, the temple-blocks, the Woodblock, and the clave generators are all basically similar. In each instance, the 68,000 ohm resistor connected to the grid, as resistor 120 in the first temple-block generator 94, compensates for production variations, including differences between individual tubes. Further, in each instance, the keying resistor, as the resistor 132 in the generator 94, slows the attack somewhat. The tom-toms could be the same as the temple-blocks, insofar as the generators are concerned, except for cir-cuit values. Similar-ly, the bass drum generator could be of the same type as the temple block generators. However, the circuits would require unduly large components, and it is for this reason that the slightly different generators of the bass drum and tom-toms are used. However, all of the percussive generators heretofore described are to a considerable extent similar.

Turning now to the lower right hand portion of FIG. l, there will be seen a noise generator 150. This noise generator is a super-regenerative detector type circuit in which the gain is so high that thermal noise is heard simply as a random noise or hiss. The term random noise as is well known in the art, refers to a sound, or electrical signal representing sound, containing a more or less complete gamut of sound frequencies. It is heard by the listener as noise having no definite musical pitch. Such random noise is not repetitive. It is sometimes known as white noise since it is of the same type that produces a white screen in the television art.

The noise generator includes a triode tube 152, the plate of which is connected through a load resistor 154 to the B+ supply line 22. The cathode is connected to a tap 155 on an inductance 156, the lower end of which is grounded. The inductance 156 is paralleled by a resistor 158, and the combination is connected through a capacitor 160 to the grid of the triode 152. The junction of the capacitor 160 with the inductance 156 and resistor 158 is grounded by a capacitor 162. The grid is connected by a shunting resistor 164 to ground. The plate further is connected through a coupling capacitor 166 to a shielded lead 168, which is shunted to ground by a capacitor 170. As will Ibe apparent, the entire noise generator is shielded, as is indicated at 170.

The noise generator operates continuously whenever the apparatus is turned on, and although the precise tuned frequency is not critical, it is conveniently on the order of 27 megacycles. By way of example, specific circuit values are as follows:

Resistor 154 100,000 ohms. Inductance156 2.25 microhenries. Resistor 158 15,000 ohms. Capacitor 160 56 micromicrofarads. Capacitor 162 27 micromicrofarads. Resistor 164 1 megohm.

Capacitor 166 .001 microfarad. Capacitor 170 390 micromicrofarads.

The shielded lead 168 is connected in parallel to a maracas amplifier 170, a brush amplifier 172, and a cymbal amplifier 174. The maracas amplifier 170 comprises a triode tube, such as one-half of a 12AX7. The previously mentioned triode generator tubes can also be of this type. The plate of this tube is connected through a resistor 176 to a collector line 178, and througha common load resistor 180 to the B+ supply line 22. The cathode is connected through a common cathode resistor 182 to ground.

The grid is connected to a grid resistor 184, which is connected to a resistor 186. The resistor 186 is connected through a resistor 188 to the shielded lead 168, and also is connected to a resistor 190. Resistor 190 is connected to ground. A grounded capacitor 192 is connected to a junction 194. The junction 194 is connected through a charging resistor 196 to the negative bias line 50, and is also connected through a resistor 198 to the junction of the resistors 184 and 186, The junction 194 further is connected to a resistor 200 which is connected to the ground-out key switch 202. This point is also connected to ground by a capacitor 204.

The amplifier 170 is normally biased off, and no sound passes through from the noise generator to the collector line 178. The capacitors and resistors heretofore set forth determine the attack and decay of the amplifier as it is keyed on by grounding out at the switch position 202. In particular, the capacitor 192 and resistor 196 determine the decay time.

The brush amplifier is similar to the maracas amplifier 170. It comprises a triode tube, the plate of which is Connected through a load resistor 206 to the collector line 178, and hence to the common rload resistor 180. The cathode is connected to the previously mentioned common cathode resistor 182.

The grid is shunted to ground by a capacitor 208, which differentiates the brush amplifier from the maracas amplier, knocking ofi some of the high frequencies. The Igrid further is connected through a resistor 210 to a capacitor 212 leading back to the junct-ion between the resistors 184 and 1.86. The junction between the capacitor 212 and resistor 210 is connected through a resistor 214 to a junction 216. This junction is grounded through a capacitor 218, and is connected through a resistor 220 to the negative bias line 50. It further is connected through a resistor 222 to a ground-out key switch 224, the latter being shunted to ground by a capacitor 226.

The cross coupling of the maracas and brush amplifiers as provided by the common cathode resistor 182 is important. The cross coupling insures that of these two amplifiers, one will be cut off immediately as another is keyed on. For example, in fast keying, if the brush amplifier were not completely cut off, and the maracas amplifier were keyed, the cross coupling would change the bias and immediately cut off the brush amplifier. In general, this circuit allows a long tail that can be cnt off at any time.

The cymbal amplifier 174 is somewhat different, using a pentode tube, such as a. 6BA6. The suppressor grid is directly connected to the cathode, and the cathode is grounded through a resistor 228. The plate is connected through a resistor 230 to the B+ supply line 22. The plate is also connected by means of a wire or the like 232, preferably including a series capacitor 231 and resistor 233, to a formant filter 234, to be discussed hereinafter. The common collector line 178 is also connected through a capacitor 236 and resistor 238 to the formant filter 234.

The second grid of the tube of the cymbal amplifier 174 is connected to a voltage divider comprising a resistor 240 connected to the B+ supply line 22, and a grounded resistor 242. A sliding tap 244 on the resistor 242 is grounded, and provides for variation of the bias on the second grid.

The control grid is connected through a capacitor 245 and a resistor 246 to the shielded lead 168, and also is connected through a resistor 248 to the negative supply line 50. In addition, the grid is connected through a resistor 250 to a junction 252, the latter being connected through a resistor 254 to the negative supply line 50. The junction 252 is connected by means of a resistor 256 to the ground-out key switch 258, which is connected or shunted to ground by a capacitor 260.

The maracas, brush and cymbal amplifiers are not filters, inasmuch as they all pass substantially the same frequencies, although, the capacit-or 208 does knock off some of the highs passed by the brush amplifier 172, as

noted.

Illustrative circuit values for the maracas, brush and cymbal amplifiers are as follows:

Resistor 176 10,000 ohms. Resistor 180 100,000 ohms. Resistor 182 1,500 ohms. Resistor 184 220,000 Ohms. Resistor 186 180,000 ohms. Resistor 188 150,000 ohms. Resistor 190 180,000 ohms. Resistor 196 2,200,000 ohms. Resistor 198 1,000,000 ohms. Resistor 200 100,000 ohms. Resistor 206 10,000 ohms. Resistor 210 220,000 ohms. Resistor 214 1,000,000 ohms. Resistor 220 2,200,000 ohms. ,Resistor 222 47,000 ohms. VResistor 228 470,000 ohms. Resistor 230 68,000 ohms. Resistor 238 47,000 ohms. Resistor 240 100,000 ohms. Resistor 242 50,000 ohms. Resistor 246 470,000 ohms. Resistor 248 3,300,000 ohms. Resistor 250 1,000,000 ohms. Resistor 254 4,700,000 ohms. Resistor 256 2,200 ohms. Capacitor 192 .047 microfarad. Capacitor 204 .01 microfarad. Capacitor 208 56 micromicrofarads. Capacitor 212 390 micromicrofarads. Capacitor 218 .082 microfarad. Capacitor 226 .01 microfarad. Capacitor 236 470 micromicrofarads. Capacitor 24S 560 micromicrofarads. Capacitor 260 .01 microfarad.

The potentiometer 242, 244 varies the screen voltage on the pentode tube of the cymbal amplifier 174 and controls the length of the tail. As will be apparent, the capacitor to ground from at or adjacent each ground out key switch of the oscillators and amplifiers heretofore set forth is for click suppression.

As has been explained heretofore, each of the various oscillators is biased into decadent oscillation upon closing ofthe key switch. However, in the case of the maracas, brush and cymbal amplifiers, each will remain conducting as long as the key switch is closed, and starts to decay only when the key is opened.

Immediately to the left of the maracas amplifier 170 and to the right `of the clave generator 146, on the schematic diagram of FIG. l, there is a shimmer generator designated generally by the numeral 262. The shimmer generator is a low frequency phase shift oscillator, oscillating on the order of 17 c.p.s. This oscillator comprises a triode tube 264, conveniently part of a twin triode shared with the clave generator. The plate of this tube is connected by a load resistor 266 to the B+ supply line 22. The plate is also connected to a feed-back capacitor 268 leading to a grounded resist-or 270, and to a capacitor 272. The capacitor 272 leads to another grounded resistor 274, and also to a capacitor 276 which is directly connected to the grid. Additionally, the grid is shunted to ground by a resistor 278. The cathode is grounded through a resistor 280 by-passed by capacitor 282.

The output of the shimmer oscillator 262 is taken through a capacitor 282 connected through the plate, and also connected to a resistor 284. The resistor 284 is connected to a modulating capacitor 286 shunted by a resistor 288, and also to a diode 290. The opposite side of the diode is shunted to ground by a resistor 292, and is also connected by a capacitor 294 to the formant filter or tank circuit 234 previously referred to. This formant filter includes a tunable inductance 296 and a capacitor 298 connected in parallel therewith. The collector line 8 232 is connected to the top of this formant filter, as previously noted, and the output therefrom is through a capacitor 300 in series with a resistor 302 leading to the output or collector line 64 previously mentioned.

The formant filter or resonant circuit 234 is normally tuned to 7500 c.p.s. However, as the shim-mer oscillator 262 oscillates, it varies the resistance of the diode 290, and this connects the capacitor 286 more or less in parallel with the formant filter, thereby varying the tuned frequency thereof at the 17 c.p.s. frequency of the shimmer generator.

The noise signal passed by all of the maracas, brush and cymbal amplifiers is impressed on the formant filter 234. The output thereof tends to sound somewhat like a hiss of air without the shimmer generator. However, the frequency modulation of the formant filter by means of the shimmer generator lends an authentic instrument sound to the outputs of the amplifiers. This will readily be understood in connection with a cymbal, since in a real cymbal the nodal points actually move, thus giving the shimmering effect. This effect is si-mulated by the shimmer generator in the present circuit.

In connection with the shimmer generator 262 and the formant filter 234, the following circuit values are set forth by way of illustration:

Resistor 266 100,000 ohms. Capacitor 268 .0068 microfarad. Resistor 270 330,000 ohms. Capacitor 272 .0068 microfarad. Resistor 274 560,000 ohms. Capacitor 276 .068 microfarad. Resistor 278 1 megohm. Resistor 280 2,700 ohms. Capacitor 282 25 microfarads, 10 volts. Resistor 284 150,000 ohms. Capacitor 286 .01 microfarad. Resistor 288 10,000 ohms. Resistor 292 33,000 ohms. Capacitor 294 .001 microfarad. Inductance 296 l0 millihenries. Capacitor 298 .0043 microfarad. Capacitor 300 220 micromicrofarads. Resistor 302 68,000 ohms.

The output or collector line 64 is connected to the input of a preamplifier stage 304 illustrated as utilizing a 6AB6 tube. The out-put of the preamplifier tube is 4coupled through a capacitor 306 to a potentiometer 308 shown within a dotted line rectangle 310. The showing is in this manner, since the potentiometer is located on an outer panel of the apparatus within convenient reach of the operator, rather than being mounted directly adjacent the preamplifier and other electronic parts. The sliding tap 312 of the potentiometer is connected to an amplifier 314, and the amplifier is connected to a loudspeaker 316.

The various ground-out key switches such as 10, 88, 92 etc. may be manually operated, and this is all that is necessary for an understanding of the circuits of the present invention. However, it is preferable that these key switches should be manually operated or, alternatively, mechanically operated by a commutator arrangement, as in the copending appiication filed Apr. 14, 1961, Ser. No. 103,001 now Patent No. 3,207,835 for Rhythm Device, filed in the names of Howard E. Holman, Joseph H. Hearne and Marvin C. Korinke, incorporated herewith by reference. When the device is switched mechanically, it may be desirable to start it in operation while other music, as on an electronic organ, is already playing. To this end, means is provided whereby the player may set the desired speed of operation and phasing thereof relative to the organ or other instrument visually, with no audible sound, until the sound is desired. Means for effecting this is illustrated at the right side of the wiring diagram of FIG. 1, under the label Tempo Light.

The tempo light actually includes two separate lamps having slightly different functions. Thus, there is a neon bulb or light 318 for indicating the rhythm or characteristic of the sound being produced, while there is an additional neon light 320 which serves simply as a metronome, indicating the rate of rhythm tone production.

The neon light 318 is controlled by a normally cut off amplifier or electric switching circuit 322 including a vacuum tube, conveniently a triode 324 of the 6C4 type. The plate of the tube 324 is connected through a load resistor 326 to the B+ supply line 22. The plate is shunted by a capacitor 328, and is connected through a resistor 330 to one side of the neon light 318. As will be apparent shortly, this side of the neon light is brought toward ground potential when the tube 324 conducts. The cathode of the tube 324 is directly grounded, while the grid is connected to a network including a resistor 323, the opposite side of which is connected to the negative bias supply line 50. The grid is also connected by a capacitor 325 to a terminal 327. This terminal is connected by a capacitor 329 to ground, and is connected through a resistor 331 to the negative bias supply line 50. The terminal 327 further is connected by means of a resistor 332 to a ground-out key switch 334, of the type heretofore discussed. The tube 322 normally is cut off, but when the switch 334 is grounded the tube is rendered conductive, thereby greatly dropping the potential on the plate, and causing the neon light 31S to fire.

The opposite side of the neon light is connected through series resistors 336 and 338 to the B+ supply line 22. The junction between these two resistors is shunted to ground by a capacitor 340. One end of the second neon light 320 also is connected to the resistor 336, in common with the light 318, and there is a connection from this -point through a capacitor 342 and a shunting resistor 344 to a jack 346.

The opposite side of the neon light 320 is connected to a resistor 348, and a resistor 350 shunts the neon light 320. The opposite end of the resistor 348 is connected to a ground-out keying switch 352, and also to a biasing network comprising a parallel connected resistor 354 and capacitor'356, the opposite end of which network is connected to ground. The neon lights and assorted connections are shown within a dotted rectangle 358, as they are physically removed from the remainder of the circuit, and disposed at a panel of the apparatus where they readily may be viewed by the player.

Illustrative values of the circuit elements just discussed are as follows:

Resistor 323 330,000 ohms. Resistor 326 1 megohm. Resistor 330 47,000 ohms. Resistor 332 47,000 ohms. Resistor 336 10,000 ohms. Resistor 338 22,000l ohms. Resistor 344 l megohm. Resistor 348 150,000 ohms. Resistor 350 68,000 ohms. Resistor 354 150,000 ohms. Capacitor 325 .047 microfarad. Capacitor 328 .047 microfarad. Capacitor 329 .01 microfarad. Capacitor 340 8. microfarad, 350 volts. Capacitor 342 .001 microfarad. Capacitor 356 .01 microfarad.

Reference has been made heretofore to the fact that the various ground out key switches may be closed manually, or yby mechanical means in accordance with a copending application. Reference should be had to FIG. 1b wherein there is a schematic showing of mechanical switching arrangement 360. This switching arrangement is connected internally with a commutator device by means of a plurality of different switching contacts whereby each of the twelve switch contacts 56, 88, 92, etc. il-

lustrated around the periphery of the device is grounded in any predetermined sequence. In accordance with any predetermined sequence, only one or more of the switch contacts may be grounded, except for the switch contact 352 which is grounded once for each measure to provide a metronome indication and the switch contact 334 which is interconnected with others of the switch contacts for grounding to indicate the rhythm as well as the beat. The mechanical switching device is provided with a great number of preselected combinations, any of which may be utilized, to provide different types of rhythms. In addition, the commutator therein is capable of being driven at variable speed, whereby to vary the speed at which the entire apparatus operates. The details of construction of the mechanical switching device 360 comprise divisible subject matter and hence are not shown herein in detail.

Various modifications of the formant filter and shimmer generator circuit are shown in FIGS. 2, 3 and 4. Similar parts are identified -by similar numerals, the suffix a being used in FIG. 2. Thus, the formant filter is indicated at 234a, including an inductance 29611. The inductance is paralleled 'by the series combination of a capacitor 360, and a voltage sensitive capacitor 362. As is well known, the capacity of a voltage sensitive capacitor changes with the bias applied thereto. A D.C. bias is applied to the junction between the capacitors through a resistor 364, and the shimmer generator 262e is connected to this same point through a resistor 28451. The bottom end of the formant filter 234a is grounded, while the signal in is connected to the top of the formant filter through a resistor 366, the signal out being taken through a resistor 368. The capacitor 360 has a low reactance at frequencies representing program material, and hence the voltage sensitive capacitor 362 has the most effect insofar as the signal in and signal out is concerned. The capacitor 360 has a high reactance at the frequency of the modulating signal from the generator 26251. Thus, the capacity of the capacitor 362 varies at the frequency of the generator 262a, thereby oscillating the resonant frequency of the formant filter 234a at the frequency of the generator 262a.

The circuit of FIG. 3 is quite similar to that of FIG. 2, the same numerals being used with the suffix b. The diference is that a capacitive diode 370 is substituted for the voltage sensitive capacitor. Such a diode requires a reverse bias, andthe program material voltage must be low relative to the D.C. bias and the modulating voltage. With proper choice of values, it is a simple matter to obtain a 2:1 ratio in capacity as the capacity of the diode varies with the application of the modulating voltage from the generator 26817. It is also possible to obtain a capacity variation of as much as 10: 1.

The circuit of FIG. 4 is similar to both FIGS. 2 and 3, similar numerals being used, with the addition of the sufiix c. In this instance, the voltage sensitive capacitor 362 of FIG. 2 has been replaced by a varistor 372. The capacitor has been moved above the varistor, but the circuit will work either way. The resistance of the varistor changes markedly with the voltage applied thereto, as determined by the D.C. bias and the generator 262e. yThis renders the capacitor 360C more or less effective, and hence varies detuning of the filter 234C.

A further modification of the formant filter and shimmer generator circuit is shown in FIG. 6. The parts in FIG. 6 are similar to those in FIG. 1, and similar numerals are used with the addition of the sufiix d. The embodiment of FIG. 6 eliminates several parts, and hence is more economical to manufacture. Thus, the plate of the tube 264d is connected directly through a capacitor 282d to the top or" the formant filter or tuned circuit 234:11. For eX- ample, the capacitor 282d might be .001 microfarad capacity. The change in plate resistance of the tube 264d during oscillation renders the capacitor 2820? somewhat more or less effective, thereby causing a certain amount of reactive detuning of the tank or formant filter 234er'. In addition, considerable amplitude modulation is provided.

In connection with all of the various embodiments of the invention as it pertains to the frequency or shimmer generator modulated formant filter, it will be observed that the modulation is of a filter serving to modify the timbre of a tone at a desired repetition rate, once the principal timbre has already been generated. In other words, this is not modulation of a generator, but formant treatment of a tone already generated.

A simple circuit is shown in FIG. for effecting reiteration of any of the desired tones, such as the bass drum, the first or second tom-tom, etc., either independently of, or in addition to the manual or mechanical keying. Thus, a phase shift oscillator 374, for example similar to the shimmer generator 262 has the output thereof coupled through a capacitor 376 and a resistor 37S to the base 380 of a transistor 382. The transistor is of the PNP type, and the emitter 384 thereof is grounded. The collector 386 is connected to la ground-out keying point indicated by the letter X. This can be any of the various ground-out key switches, such as 56, 88, 92, etc., as may be desired. In fact, one such switching circuit may be provided for each of these key switches, if desired, with a separate phase shift oscillator for each. The frequency of such oscillator may be varied if desired. In this instance, the transistor 382 serves as an electronic switch, and provides a square wave output. However, this is not necessary, since other wave shapes and other types of transistors would be suitable to perform this keying function.

1n accordance with the present invention, generators have been disclosed for simulating the effects of a bass drum, tom-toms, temple blocks, wood blocks, claves, maracas, brushes, and cymbals, automatically or manually, and all in a relatively small package. Accordingly, a performer on an electronic organ or the like playing a melody, can easily provide himself with a rhythm accompaniment at modest cost, and without the necessity of an assistant.

The various circuits and structures shown and described are by way of illustration only. Various changes will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar an they fall within the spirit and scope of the appended claims.

The invention is hereby claimed as follows:

1. Apparatus for producing percussive musical effects comprising a damped oscillator normally biased to nonoscillating condition, first keying means for keying said oscillator to bias it for decaying oscillation, a source of a wide range of audio-frequency electrical energy, an amplifier connected to said source, means normally biasing said amplifier beyond cut off, second keying means for keying said amplifier to conduct said wide range of audio-frequency electrical energy, a common amplifier, means for connecting said common amplifier to said damped oscillator and to said first mentioned amplifier, and electro-acoustic translating means connected to said common amplifier.

2. Apparatus as set lforth in claim 1 wherein at least one of said keying means comprises .a capacitor, means for charging said capacitor, land means for discharging said capacitor for producing a decaying bias.

3. Apparatus as set forth in claim 2 and further including means for normally charging one end of said capacitor negative, and means for substantially grounding said end of said capacitor, whereby to produce a positive pulse at the other end thereof.

4. Apparatus as set forth in claim 3 wherein the source of a wide range of audio-frequency electrical energy comprises a source of electrical noise.

5. Apparatus for producing percussive musical effects comprising a yplurality of substantially similar damped oscillators each normally biased to non-oscillating condition, first keying means for selectively keying said oscillators selectively to bias said oscillators respectively for decaying oscillation, said oscillators being respectively tuned to a plurality of different frequencies, a source of a Wide range of audio-frequency electrical energy, an amplifier connected to said source, means normally biasing said amplifier beyond cut off, second keying means for keying said amplifier to conduct said wide range of audio-frequency noise, a common amplifier, means connecting said common amplifier to said damped oscillators and to said first mentioned amplifier, and electroacoustic translating means connected to said common amplifier.

v6. Apparatus as set forth in claim 5 wherein there is provided a plurality of amplifiers connected to said source and to said common amplifier, said plurality of amplifiers each having attack and decay characteristics, corresponding characteristics of at least some of said amplifiers being different.

7. Apparatus .asset forth in claim 6 wherein the means connecting the plurality of amplifiers to the common amplifier comprises a common formant filter.

8. Apparatus as set forth in claim 7 and further including means for cyclically modulating said filter.

9. Apparatus for producing musical effects comprising a source of a wide band of audio-frequency electrical energy, an output system connected to said source, a parallel resonant circuit, means connecting said parallel resonant circuit in shunt with said source, reactance means, cycli-cally operable electrically variable impedance means, means connecting said reactance means and Said electrically variable impedance means in series with one another and in parallel with said parallel resonant circuit, and electrical means for electrically cyclically varying said electrically variable impedance means cyclically to vary the effect of said reactance means on said parallel resonant circuit, and thereby cyclically to vary the tuning of `said parallel resonant circuit.

10. Apparatus as set forth in claim 9 wherein the means for rendering the reactance means of greater and lesser effect comprises a unilaterally conducting device, and means for varying the bias on said unilaterally conductive device.

11. Apparatus as set forth in claim 9 wherein the means for rendering the reactance means of greater and lesser effect .comprises a voltage sensitive capacitor.

12. Apparatus as set forth in claim 9 wherein the means for rendering the reactance means of greater and lesser effect comprises a capacitive diode.

13. Apparatus as set forth in claim 9 wherein the means for rendering the reactance means of greater and lesser effect comprises a varistor.

14. Apparatus for producing percussive musical effects comprising a damped oscillator normally biased to non-oscillating condition, means for keying said oscillator to bias it for decaying oscillation, a source of a Wide range of audio-frequency electrical energy, an amplifier connected to said source, means normally biasing said amplifier beyond cut off, means for keying said amplifier to conduct said wide range of audio-frequency electrical energy, a common amplifier, means connecting said common amplifier to said damped oscillator and to said first mentioned amplifier, electro-acoustic translating means connected to said common amplifier, land electronic repeater means connected to at least one of said keying means for cyclically operating said keying means.

15. Apparatus for producing percussive musical effects comprising a source of wide range audio-frequency energy, a plurality of amplifiers respectively connected to said source, at least two of -said amplifiers comprising vacuum tube amplifiers having a common cathode resistor, means respectively biasing said amplifiers to cutoff, means for respectively rendering said amplifiers conductive, each of said amplifiers having attack and decay characteristics, corresponding chanacteristics of different amplifiers being different, common output means for said amplifiers comprising a formant filter, and means for cyelically detuning said filter, and electro-acoustic translating means connected to said common output rneans. 16. Apparat"ffor producing percussive musical effects cornprisi a plurality of substantially similar damped phase fshift oscillators respectively tuned to a plurality of different frequencies and each normally biased to non-oscillating condition, selective keying means for selectively supplying a bias to said phase shift oscillators, said keying means including switch meansland bias control means voperative upon operation of said switch means and immediately operative irrespective kof continued operation of said switch means to provide a decaying bias respectively to .cause said phase shift oscillators to oscillate in decaying fashion, an amplifier, means connecting said phase shift oscillators to said amplifier, and electro-acoustictranslating means connected to said amplifier.

17. Apparatus Vas set forth in claim 16 wherein the selective keyingjrneans comprises a plurality of capacitors respectively connected t-o said phase shift oscillators, means normallybiasing all of said capacitors negative on the side opposite said phase shift oscillators, means for substantially grounding the negative side of each of said capacitorsl'selectively whereby to apply a positive charge selectively to said phase shift oscillators, and

means including a resistive path for selectively discharging said capacitor-s after grounding of the negative side thereof.

18. Apparatus for producing percussive musical effects comprising a damped oscillator normally biased to non-oscillating condition, iirst keying means for keying said oscillator to bias it for decaying oscillation, a source of a Wide range of audio-frequency electrical energy, an electronic gate connected to said source, means normally biasing said electronic gate beyond cut off, second keying means for keying said electronic gate to conduct said wide range of audio-frequency electrical energy, output means, and means for connecting said `output means to said electronic gate and to said damped oscillator.

References Cited UNITED STATES PATENTS 2,342,338 2/1944 Henert 84l.26 X 2,926,347 2/1960 Thiele 331--172 X 3,141,919 7/1964 Mabuchi 84-1.26

ARTHUR GAUSS, Primary Examiner. DAVID J. GALVIN, Examiner. D. D. FORRER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,358,069 December l2, 1967 Joseph H. Hearne It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 72, for "os connected" read s connected Column 4, line 3, for "circuit Value" read circuit values Column 8, line 32, for ".068 mcrofarad" read .0068 mcrofarad line 4l, for "1() millhenres" read 100 mllhenries column l2, line 40, for "conductive" read conducting Signed and sealed this 25th day of February 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

14. APPARATUS FOR PRODUCING PERCUSSIVE MUSICAL EFFECTS COMPRISING A DAMPED OSCILLATOR NORMALLY BIASED TO NON-OSCILLATING CONDITION, MEANS FOR KEYING SAID OSCILLATOR TO BIAS IT FOR DECAYING OSCILLATION, A SOURCE OF A WIDE RANGE OF AUDIO-FREQUENCY ELECTRICAL ENERGY, AND AMPLIFIER CONNECTED TO SAID SOURCE, MEANS NORMALLY BIASING SAID AMPLIFIER PLIFIER BEYOND CUT OFF, MEANS FOR KEYING SAID AMPLIFIER TO CONDUCT SAID WIDE RANGE OF AUDIO-FREQUENCY ELECTRICAL ENERGY, A COMMON AMPLIFIER, MEANS CONNECTING SAID COMMON AMPLIFIER TO SAID DAMPED OSCILLATOR AND TO SAID FIRST MENTIONED AMPLIFIER, ELECTRO-ACOUSTIC TRANSLATING MEANS CONNECTED TO SAID COMMON AMPLIFIER, AND ELECTRONIC REPEATER MEANS CONNECTED TO AT LEAST ONE OF SAID KEYING MEANS FOR CYCLICALLY OPERATING SAID KEYING MEANS. 